The miniaturization of electronic components has permitted the reduction of the volume requirements for control structures. While the miniaturization is normally accompanied with a reduced heat load, cooling of the electronic components is still normally required. The compactness permitted by miniaturization can complicate the cooling process. Additionally, the control structures can be located in conjunction with other structures which are located so as to minimize space requirements.
Transport refrigeration equipment, for example, must be located between the cab of the truck and the trailer while permitting the necessary relative movement between the truck and trailer. The refrigeration equipment must be external to the trailer so as to avoid reducing the cargo volume available and must present a streamlined profile to minimize wind resistance. Superimposed upon this is the need to provide more cooling capacity within the available space as trailer lengths and therefore the cooling requirements increase. It is desirable to locate the electronic controls in proximity to the devices being controlled such as valves, clutches, and motors in order to reduce the length, and cost, of the connecting electric harness. In placing such electronic controls near the devices being controlled, they are often placed in a harsh, high temperature environment, such as the engine compartment of a refrigeration unit, as well as near heat sources such as engines and compressors which may cause temperatures to exceed the allowable limits for the electronic controls.